In recent years, there has been a rapid and extensive development of intelligent devices. A non exhaustive list of such devices are laptops, personal digital assistants (PDA:s), digital notebooks, play-gadgets, mobile phones, land-radios (e.g. walkie-talkies) etc.
Requirements have been placed on such intelligent devices, especially handheld devices, to have a compact, highly integrated and small sized design. At the same time it is frequently required that these devices support the addition of new functionality. However, it is usually difficult to accomplish addition of new functions, especially if a function requires additional hardware, since the compact design leaves little or no space for addition of new extra hardware. If the extra hardware can be added at all it is usually associated with costly design changes.
In this connection it is well known to attach exterior accessory modules to a device for providing the device with an additional functionality. Such accessory modules are usually attached to the device through a connector, e.g. a connector arranged at the lower end of a mobile phone. Typically, these accessory modules operate essentially independently from the device attached upon. For example, an accessory module may only require electrical power from the device, whereas the function provided by the module is essentially executed within the module it self and then subsequently delivered to the device. Conversely, the device is typically designed to operate independently from any accessory module, i.e. the device can operate with or without any accessory module.
A few examples may be clarifying. A module comprising an MP3-player may be attached to a PDA for supplying recorded music to the PDA, without the need for any processing assistance from the PDA. Likewise, a module comprising a radio may be attached to a mobile phone for supplying radio broadcasts to the mobile phone without the need for any processing assistance from the phone. Similarly, a module comprising a hands-free function may be attached to a mobile phone, where the module may transmit and receive signals to and from a wireless headset without any processing assistance from the phone. Consequently, the new functionality is provided by the attached module and subsequently delivered to the device, whereas the device itself can remain unchanged regardless of any attached module, which is an important advantage in many applications.
However, exterior accessory modules show considerably drawbacks, especially in connection with compact, highly integrated and small sized devices. A compact design makes it difficult to accomplish a firm and strong mechanical connection between the device and an exteriorly attached accessory module. An attached module may therefore fit rather loosely to the device. This increases the risk for an intermittent electrical contact between a module and the device, especially in harsh environments. A weak mechanical connection between device and module may even enable forces in a harsh environment to rip the module off the device, especially when the module is attached to the exterior of the device. The requirements for a compact mechanical construction may also diminish the possibility to accomplish a environment proof connection between an exterior module and the device, which means that dust and humidity may affect the electrical connectors of the device and the module. Another problem with known exterior accessory on modules is that a detached module usually leaves the mechanical and electrical connectors of the device openly exposed to the environment. The connectors may then be scraped, deformed, fractured, corroded, or otherwise damaged so that the device becomes unable to function with a module.
In addition to the exterior accessory modules as mentioned above there are other more or less interior accessory modules for providing a device with a range of new functionalities. One example is the so-called PCMCIA-card (Personal Computer Memory Card International Association) and other similar small circuit boards. Such small circuit boards are normally inserted into the device through a slot arranged on the device, e.g. at the side of a laptop, or even to a PDA or mobile phone. An interior PCMCIA-card or similar does not show the same exposure to the environment as previously described exterior modules. Mechanical forces may in particular have less impact on such cards, since they are mechanically protected by the device to which they are inserted. However, the slot through which such a card is inserted is often left open when the card is taken out. The recess in which the card is received will then be exposed to the environment and particles, fluid (e.g. water), humidity or similar can then easily assemble in the recess to affect electrical and mechanical connectors. Particles may for example block mechanical and electrical connectors and water or humidity may cause corrosion on the electrical connectors, etc.
Moreover, the general idea to attach an exterior or interior module to a device inevitably makes the device bulkier, which is totally opposite to the requirements for a compact, highly integrated and small sized design.
There is consequently a need for an exchangeable module that provides an additional functionality to a device, which module is large enough to comprise additional hardware needed for the additional functionality, and where the module can be connected to the device to form a compact, highly integrated and small sized apparatus possessing a good protection from the environment. It is also preferred that the module supports a proper modular design so that the device can remain essentially unchanged regardless of the module currently used.